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1 Danang University of Technology
Chng 2 C TNH C V CC
TRNG THI LM VIC CA NG C IN
2 Danang University of Technology
2.1 Khi nim chung
Trong chng 1 cho ta thy, khi t 2 ng c tnh c
M() v Mc() ln cng mt h trc ta , ta c th xc nh
c trng thi lm vic ca ng c v ca h truyn ng
in.
Trng thi xc lp khi M = Mc ng vi giao im ca 2 ng
c tnh M() v Mc() .
Trng thi qu khi M Mc v tc cha t n xc lp:
xl.
3 Danang University of Technology
Khi phn tch cc h truyn ng in, ta thng coi my sn
xut cho trc, ngha l coi nh bit trc c tnh c
Mc() ca n. Vy mun tm kim mt trng thi lm vic vi
nhng thng s yu cu nh tc , mmen, dng in ng
c, ta phi to ra nhng c tnh c ca ng c tng
ng. Mun vy, ta phi nm vng phng trnh c tnh c
v cc c tnh c ca cc loi ng c in, t hiu c
phng php to ra cc c tnh c nhn to ph hp vi
my sn xut cho. T ta iu khin ng c sao cho c
c cc trng thi lm vic theo yu cu cng ngh.
4 Danang University of Technology
Phn cm: To ra t trng
Phn ng: phn chuyn
ng quay
2.2 c tnh c v cc trng thi lm vic ca ng cin mt chiu kch t c lp
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5 Danang University of Technology
2.2.1 Phng trnh c tnh c ch xc lp
6 Danang University of Technology
7 Danang University of Technology 8 Danang University of Technology
2.2.2 nh hng ca cc thng s in i vi c tnh c
1, Trng hp thay i in tr ph mch phn ng
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9 Danang University of Technology
2, Trng hp thay i in p phn ng
10 Danang University of Technology
3, Trng hp thay i t thng kch t
11 Danang University of Technology
2.2.3 M my (khi ng) ng c in mt chiu kch t clp
12 Danang University of Technology
2.2.4 o chiu quay ng c
Mun o chiu quay ca ng c in mt chiu ta c th thc hin mt trong
hai cch:
+ o chiu t thng.
+ o chiu dng in phn ng.
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13 Danang University of Technology
c tnh c khi o chiu i xng nhau qua gc ta .
14 Danang University of Technology
2.2.5 Cc trng thi hm ca ng c in mt chiukch t c lp
Hm mt h thng T nhm mc ch:
Dng h T.
Gi h thng ng yn khi h thng ang chu mt lc c xu
hng gy chuyn ng.
Gim tc h T.
Ghm cho h T lm vic vi tc n nh. V d: gi tc
u khi xe in xung dc, khi h vt cu cn trc,..
15 Danang University of Technology
Cc trng thi hm ca ng c:
Hm ti sinh
Hm ngc
Hm ng nng
c im chung ca c 3 trng thi hm: ng c u lm vic
ch my pht, bin c nng ca ng c ang c qua ng c
thnh in nng tr v li (hm ti sinh) hoc tiu th thnh dng
nhit trn cc in tr hm (hm ngc, hm ng nng).
16 Danang University of Technology
a) Hm ti sinh
Xy ra khi tc quay ca ng c ln hn tc khng ti ltng >0.
ng c lm vic nh mt my pht song song vi li v trnng lng v ngun.
IU E
R
K K
R
M K I
h
h h
0 0
0
M
o
UE
I
U
I
E
M C
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17 Danang University of Technology
Mt s trng hp xy ra hm ti sinh:
1) Hm ti sinh khi c ng lc quay ng c: My sn xut l ngun nglc quay rotor ng c, lm >0.
Dng in i chiu Mmen do ng c sinh ra ngc vi chiu chuynng ca ng c ang c tr thnh mmen hm ng c.
18 Danang University of Technology
2) Hm ti sinh khi gim in p phn ng: Mc l dng mmen th nng.in p ngun gim t ngt lm 0 gim trong khi cha kp gim. ng nngtch ly tc cao s tun vo ng c v bin ng c thnh my pht tr nnglng v ngun.
19 Danang University of Technology
3) Hm ti sinh khi o chiu in p phn ng: Mc l dng mmen th nng h ti.
M C
o
M
Mk
o
AM
M
c
M
M
Nng ti
H ti
c
B
c
d
20 Danang University of Technology
b) Hm ngcXy ra khi mmen hm ca ng c ngc chiu tc quay. Hai trng
hp ca hm ngc:
1) a in tr ph ln vo mch phn ng:
hh
pu
u
pu
uuh
IKM
RR
KU
RR
EUI
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21 Danang University of Technology
2) Hm ngc bng cch o chiu in p phn ng:
IU E
R R
U K
R R
M K I
hf f
h h
< 0
0
=-
-U
K KM f
R + R
( )2
22 Danang University of Technology
c) Hm ng nng (U = 0)
1) Hm ng nng kch t c lp:ng c ang lm vic vi li in, thc hin ct phn ng ng c ra khi li
in v ng vo mt in tr hm Rh. Do ng nng tch ly trong ng c nn nvn quay v n lm vic nh mt my pht bin c nng thnh nhit nng trn intr hm v in tr phn ng.
R + R h( )K
M 2
Phng trnh c tnh c:
E K
IE
R R
K
R R
M K I
hd hd
hdhd
h
hd
h
hd hd
< 0
0
Thi im hm ban u:
a
1
Mc
o
M
2
M h2 M h1
b2 b1
c1
c2
Rh2Rh1
0
+
kt
E
I h
KT R
-
Rh
23 Danang University of Technology
2) Hm ng nng t kch t:ng c ang lm vic vi li in, thc hin ct c phn ng v phn kch t
ca ng c ra khi li in v ng vo mt in tr hm Rh.
Phng trnh c tnh c:
h1h2M M
1
2
0 M
c1
c2
cM
b1
R
b2
h2
h1R
oa
KT
Rh
h I
E
Ikt
R +R
R
h
h
.
( )
R
R
KM
kt
kt2
24 Danang University of Technology
2.4 ng c in xoay chiu 3 pha khng ng b
2.4.1 Cu to v nguyn l hot ng
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25 University of Ulsan(UoU)
ng c rto dy qun
Hp u
dyChi than
v gi
Np my bi Vt nh v
Rto dy
qun
Vnh trtStato
Np my
bo v vnh
trt
Qut gi
Np qut gi
26 Danang University of Technology
ng c KB rotor dy qun
Cu to ca ng c 3 pha KB rotor dy qun
27 Danang University of Technology
Cu to ca rotor lng sc v trc quay
Cu to lng sc ca rotor
ng c rto lng sc
28 Danang University of Technology
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29 University of Ulsan(UoU)
u dy
230 V
400 V
u sao
Tam gic
30 Danang University of Technology
- Nh bit trong vt l, khi cho dng in 3 pha vo 3 cun dy t
lch nhau 1200 trong khng gian th t trng tng do 3 cun dy to ra l
mt t trng quay. Nu trong t trng quay ny c t cc thanh dn in
th t trng quay s qut qua cc thanh dn in v lm xut hin mt sc
in ng cm ng trong cc thanh dn.
- Ni cc thanh dn vi nhau v lm mt trc quay th trong cc thanh
dn s c dng in (ngn mch) c chiu xc nh theo quy tc bn tay
phi. T trng quay li tc dng vo chnh dng cm ng ny mt t lc
c chiu xc nh theo quy tc bn tay tri v to ra mt mmen lm quay
lng tr v cc thanh dn theo chiu quay ca t trng quay.
31 Danang University of Technology
Cc gi thit:
+ Ba pha ca ng c l i xng.
+ Cc thng s ca mch khng thay i ngha l khng ph thuc
vo nhit , tn s, mch t khng bo ha nn in khng khng
thay i,
+ Tng dn ca mch vng t ha khng thay i, dng t ha
khng ph thuc ti m ch ph thuc in p t vo stator.
+ B qua cc tn tht ma st, tn tht trong li thp.
+ in p li hon ton sin v i xng.
32 Danang University of Technology
Cc i lng mch stator: U1, I1, R1, .
Cc i lng mch rotor: U2, I2, R2, .
,60 1p
fn0 =
Tc t trng quay (tc ng b, tc khng ti ltng):
p
fn 100
2
60
2 ..
(vg/phut)
(rad/s)
H s trt:
0
2
0
20
0
20 1
n
nns
Dng in cm ng trong rotor cng l dng xoay chiu vi tn s xc nhqua tc tng i ca rotor vi t trng quay:
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33 Danang University of Technology
2.4.2 Phng trnh c tnh c
S thay th 1 pha pha stator: Cc i lng in mch rotor quy i v stator.
+
-
X1 R1
X
R
m
m
X'2
R'22
I1I'2
oI
s
I2 = KII2
X2 = KxX2
R2 = KRR2
KE = E1ph,m/ E2ph,m
KI = 1/ KE
KR = KX = KE/KI = K2E
I0 : Dng in t ha ca ng c
Rm : in tr mch t ha
Xm : in khng mch t ha
34 Danang University of Technology
T s thay th 1 pha pha stator, tnh dng in rotor quy iv stator:
2212
21
1
2
''
'
XXs
RR
UI
ph
Khi ng c hot ng, cng sut in t P12 t stator chuyn sangrotor thnh cng sut c Pc v cng sut nhit t nng cun dy:
P12 = Pc + P2
Nu b qua tn tht ph th c th coi mmen in t ca ng cbng mmen c:
Mt = Mc = M
35 Danang University of Technology
Cng sut in t:P12 = M0 = M + P2
0
2
0
2
.s
PPM
=>
Cng sut nhit trong cun dy 3 pha:
P2 = 3R2I22
2
2
210
2213
nm
ph
Xs
RRs
RUM
'
'
=>
Xnm = X1 + X2 : in khng ngn mch
36 Danang University of Technology
2
2
210
2213
nm
ph
Xs
RRs
RUM
'
'
Phng trnh c tnh c ca ng c KB biu din mi quan h:M = f(s) = f(s()).
0A
Mmm
M
th
sth
s
K
BMth
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37 Danang University of Technology
ng c tnh c c im cc tr gi l im ti hn K.
0A
Mmm
M
th
sth
s
K
BMth
0ds
dM
221
'2
nmXR
R
sth =
)( 22110
21
2
3
nm
ph
XRR
U
Mth =
Xt trong gii hn 0 < s < 1, ccphng trnh trn mang du + .
KB: on khi ng.KA: on c tnh lm vic ca ng c.
38 Danang University of Technology
N (Rotor speed)
Ns = Synchronism
StatorRotor
Motor C = 0
Nn = Nominal
StatorRotor
Motor C = NominalResistive C = nominal
StatorRotor
Motor C = Maximum
Resistive C = Maximum N = minimum stable one
C (torque)
Motor C
Resistive C
StatorRotor
Motor C = Faulty
Resistive C = Excessive
N = Unstable
HEATING
SNominal
Maximum C
Startup C
c tnh mmen tc
39 Danang University of Technology
2.4.3 nh hng ca cc thng s in i vi c tnh c
p
f120 =
sth = 221
2
nmXR
R
'
)( 22110
21
2
3
nm
ph
XRR
U
Mth =
ng c tnh c ca ng c KB c xc nh bi:
40 Danang University of Technology
2.4.3.1 nh hng ca in tr mch rotor R2
Trng hp ny ch thc hin c vicc ng c rotor dy qun.
sth
s
0
th
A
thMM
~
R'2
0 =
sth = 221
2
nmXR
R
'
)( 22110
21
2
3
nm
ph
XRR
U
Mth =
Khng i
Thay i ~ R2
Khng i
p
f12
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41 Danang University of Technology
2.4.3.2 nh hng ca in tr, in khng mch stator: X1, R1
0 =
sth = 221
2
nmXR
R
'
)( 22110
21
2
3
nm
ph
XRR
U
Mth =
Khng i
Thay i gim
Thay i gim
p
f12
R1
~
R'2
~
X1
42 Danang University of Technology
2.4.3.3 nh hng ca s i cc p
0 =
sth = 221
2
nmXR
R
'
)( 22110
21
2
3
nm
ph
XRR
U
Mth =
Thay i
Thay i
p
f12
Thay i
Thng thng, loi ng c ny c ch to vi cun cm stator c nhiu u
dy ra c th thay i cch u dy tng ng vi s i cc. Ty theo kh
nng i ni m ng c c 2, 3, 4, cp tc .
Do s i cc thay i nh i ni cun cm stator nn cc thng s nh in p
pha, in tr stator v in khng stator u thay i.
43 Danang University of Technology
2.4.3.4 nh hng ca tn s f1
Khi thay i f1 th tc ng b 0 s thay i, ng thi X1, X2cng b thay i, ko theo c s thay i ca c trt ti hn sthv mmen ti hn Mth.
1
1
fsth ~ 2
1
1
fMth ~
gi t trng khe h l hng s th:
constf
U
1
1
vng f1>f1m th khng c tng inp ngun cp m phi gi U1ph = const
44 Danang University of Technology
2.5.4 Khi ng ng c khng ng b
Nu khi ng ng c KB bng cch ng in trc tip vo ng
c th do lc u ng c cha quay, trt ln nn sut in ng cm
ng v dng in cm ng ln.
Dng in khi ng c gi tr c bit ln cc ng c cng sut
trung bnh v ln, to ra nhit t nng ng c v gy xung lc c hi
cho ng c.
Tuy dng in m my ln nhng mmen m my li nh.
V vy, cn phi c bin php m my gin tip i vi nhng ng c
cng sut trung bnh v ln. Mc ch: Hn ch dng in v tng mmen
m my.
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45 Danang University of Technology
2.5.4.1. Phng php m my dng in tr ph mch rotor
Phng php ny ch s dng c i vi ng c rotor dy qun.
KB
K3
K2
K1
R3
R2
R1
~
2C thMM M
0 A
2M
TN
3
2
1
a
bc
de
fg
46 Danang University of Technology
2.4.4.2. Phng php m my dng in tr hoc in khng ni tip trong mch stator
bac
~ 3
K1 K2 K2 K2K1 K1
R1 R1 R1
bac
K1
X1 X1
K1K2
~ 3
K2 K1
X1
K2
47 Danang University of Technology
2.4.4.3. Phng php m my dng MBA t ngu
bac
K KK
~ 3
K'
K'
BATN
CD
2.4.4.4. Phng php m my bng i ni Y -
48 Danang University of Technology
2.4.5 o chiu quay ng c khng ng b
CDA
CDB
a bc
o chiu quay ng c KB, cn o chiu ca t trng quay do stator
to ra. Mun vy, ch cn o 2 pha bt k trong 3 pha in p ngun cp ca
stator.
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49 Danang University of Technology
2.4.6 Cc c tnh c khi hm ng c KB
2.4.6.1 Hm ti sinh
ng c KB xy ra hm ti sinh khi tc ca ng c ln hn tc
ng b: > 0. Khi xy ra hm ti sinh th ng c lm vic nh mtmy pht v c tr nng lng v ngun.
F
N
K'
K
MM
s
s
s=0
thF
ths
s=1
thF th
221
2
nm
th
XR
Rs
'
)( 22110
21
2
3
nm
ph
th
XRR
UM
50 Danang University of Technology
2.4.6.2 Hm ngc
Hm ngc l khi mmen ca ng c ngc chiu vi tc quay. Hm ngcc 2 trng hp:
a) Hm ngc bng cch a in tr ph ln vo mch rotor
MC Mth
0
AA
B
D
E
MB
1
2
E
M
A
P
CM
M
P
M
A
MC
R
K
KB
~
K
p
51 Danang University of Technology
MC Mth
0A
AB
D
E
MB
1
2
E
M
A
P
CM
M
P
M
A
MC
R
K
KB
~
K
p
52 Danang University of Technology
b) Hm ngc bng cch o chiu t thng stator
CM MthM
1
0 A
MC
ED
D'
B B'
23
E'
E
CM
M
F
M
C
M
M
MC
KK
pR
KB
~
Ti im D nu ti l ma st th ng c s dng li khi ct in. Nu l ti th nng, ng c s tip tc o chiu quay v lm vic n nh ti im E.
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53 Danang University of Technology
2.4.6.3 Hm ng nng
hm ng nng mt ng c in KB ang lm vic ch ng c, ta phi
ct stator ra khi li in xoay chiu ri cp vo hai pha ca stator dng in mt
chiu kch t.
54 Danang University of Technology
+
- -
+ +
-
+
-
+
-Cc cch cp kch t mt chiu cho cun stator 3 pha khi hm ng
nng ng c KB
c tnh c khi hm ng nng ng c KB
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2.6. BI TP NG DNG
56 Danang University of Technology
Bi 1: Cho ng c in mt chiu kch t c lp c cc s liu k
thut sau:
Pm = 2,2 kW; Um = 110V; Im = 25,6A; nm = 1430 vg/pht; R =
0,47;
a) Hy v c tnh c t nhin ca ng c.
b) Hy v c tnh c nhn to khi c in tr ph mc
trong mch phn ng l Rf = 0,78;
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57 Danang University of Technology
Bi 2: Cho ng c in mt chiu kch t c lp c cc
s liu k thut sau:
Pm = 16 kW; Um = 220V; Im = 70A; nm = 1000
vg/pht; R = 0,28;
ng c ang lm vic vi cc thng s in l nh mc
v c in tr ph mc thm trong mch phn ng bng Rf
= 0,52. Xc nh tc quay ca ng c khi mmen
trn trc ng c bng 0,6.Mm?
58 Danang University of Technology
Bi 3: Tm tr s cc cp in tr m my ca ng c
in mt chiu kch t c lp c cc thng s k thut
sau:
Pm = 13,5 kW; Um = 110V; Im = 14,5A; nm = 1050
vg/pht;
Chn dng in khi ng ln nht Imax = I1 = 2.4Im,
dng in khi ng nh nht Imin = I2 = 1.2Im, m my
vi 3 cp in tr.
59 Danang University of Technology
Bi 4: Hy xc nh ch s in tr ph cn thit ng
vo phn ng ng c in mt chiu kch t c lp khi
hm ng nng dng in hm ban u bng 2.Im. Bit
rng trc khi hm ng c lm vic vi ph ti nh
mc.
Cc s liu k thut ca ng c: Pm = 46,5kW; Um =
220V; Im = 23,8A; nm = 1500 vg/pht;
60 Danang University of Technology
Bi 5: Cho ng c in mt chiu kch t c lp c cc s liu k
thut sau:
Pm = 34 kW; Um = 220V; Im = 178A; nm = 1580 vg/pht; R =
0,042.
ng c ang lm vic trn c tnh c t nhin vi mmen cn
trn trc Mc = Mm, dng my ngi ta chuyn sang ch hm
ngc bng cch o chiu in p v trong mch phn ng mc
thm in tr ph Rf = 1,25..
Hy xc nh tr s mmen in t ca ng c sinh ra u v
cui qu trnh hm?
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61 Danang University of Technology
Bi 6: ng c in mt chiu kch t c lp c cc
s liu k thut sau: Pm = 4,2 kW; Um = 220V; Im =
22,6A; nm = 1500 vg/pht; R = 0,841.
ng c ang lm vic vi cc thng s nh mc,
mmen cn trn trc bng nh mc v t thng kch t
ca ng c bng 0,5m. Hy xc nh tc quay v
dng in phn ng ca ng c?
62 Danang University of Technology
Bi 7: Xc nh tr s in tr ph cn thit t vo mch
phn ng ca ng c in mt chiu kch t c lp lm
vic trong ch hm ng nng cho khi dng in trong
mch phn ng bng nh mc th tc ng c bng
0,5m.
Cho cc thng s k thut: Pm = 1,6kW; Um = 110V; Im =
19,7A; nm = 970 vg/pht; R = 0,6.
63 Danang University of Technology
Bi 8: Cho ng c in mt chiu kch t c lp lm
vic ch my pht tr nng lng v li (hm ti
sinh).
Hy xc inh tc quay ca phn ng nu I = 60A, Rf
= 0.
Cc thng s k thut ca ng c:
Pm = 29kW; Um = 440V; Im = 79A; nm = 1000 vg/pht;
R = 0,278.
64 Danang University of Technology
Bi 9: Xc nh tr s ban u ca dng in phn ng khi
ct phn ng ca ng c in mt chiu kch t c lp ra
khi li in v ng kn vo mt in tr 6. Trc khi
ct ng c lm vic vi mmen M = 34,4Nm v t thng
l nh mc.
Cho cc s liu k thut ca ng c:
Pm = 6,5kW; Um = 220V; Im = 34,4A; nm = 1500
vg/pht; R = 0,14.
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65 Danang University of Technology
Bi 10: Cho mt ng c xoay chiu 3 pha khng ng b c cc s liu k thut nh
sau: Pm = 22kW, U1ph = 220V, nm = 1755 vg/pht, s i cc p = 4, tn s ngun cp f1 =
50Hz, Im = 75A, R1 = 0.044, R2 = 0.0252, in cm cun dy stator L1 = 0.55mH, in
cm cun dy rotor L2 = 0.47mH, h cm Lm = 12.9mH. H s quy i in p KE = 1.8.
iu kin v gii hn lm vic ca ng c: |u1| 220V, |i1| 75A. Tc ln nht nmax
= 6000 vg/pht.
1) Hy xc nh trt nh mc.
2) V ng c tnh c ca ng c.
3) ng c lm vic ch V/F=const. Bin in p ca stator t l vi in p
ngun cp cho n gi tr ti a 50Hz. di iu chnh tn s trn 50Hz, in p ngun
c gi nguyn in p pha 220V. Hy v cc c tnh c khi tn s thay i t 5Hz n
170Hz vi khong thay i l 15Hz.
66 Danang University of Technology
THANK YOU FOR YOUR ATTENTION!